3n concatenated with itself.

Terms

a(0) =33a(1) =66a(2) =99a(3) =1212a(4) =1515a(5) =1818a(6) =2121a(7) =2424a(8) =2727a(9) =3030a(10) =3333a(11) =3636a(12) =3939a(13) =4242a(14) =4545a(15) =4848a(16) =5151a(17) =5454a(18) =5757a(19) =6060a(20) =6363a(21) =6666a(22) =6969a(23) =7272a(24) =7575a(25) =7878a(26) =8181a(27) =8484a(28) =8787a(29) =9090